Interlock system



April 12, 1966 E. H. coMsTocK, JR, ET 3,246,178

INTERLOCK SYSTEM Filed July 25, 1963 United States Patent 3,246,178 INTERLOCK SYSTEM Eldred H. Comstoek, Jr., Laurel, and John .I. Gerding, Towson, Md., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed July 25, 1963, Ser. No. 297,729 3 Claims. (Cl. 307-94) The present invention relates to an interlock system and more particularly to an electrical interlock device for use in a high voltage system having a plurality of power supplies that each supply a plurality of module loads.

Various safety systems have been employed in the past that require the operation or movement of various parts before access may be had to a major piece of equipment. In one type of generally known interlock system, disconnect switches associated with a circuit breaker are interlocked in such a manner as to require the circuit to be opened at the circuit breaker before access could be had to the switches. After the circuit is opened, the breaker is locked open and then the associated disconnect switches are locked open, in sequence. The breaker can then be unlocked to permit testing or repairing. This type of interlock system requires a lock for each movable part and the locks are so related that each piece of equipment is locked in its safety position before a key can be released to operate a succeeding look.

A variation of the above-described interlock system is shown in US. Patent 2,166,061, which issued July 11, 1939, to Ralph L. Kirk. This patent describes an interlock system in which the keys for unlocking the several devices are released upon the successive actuation of the devices in predetermined order. When applied to a circuit breaker system, the device described in the patent provides an interlock which may be actuated to obtain isolation of the circuit breaker by locking open both disconnecting switches when work is to be done upon the circuit breaker itself. Also, the system will permit reclosing of the circuit breaker after locking open one disconnecting switch.

An interlock system that is specifically designed for protecting personnel from the dangers of .a high voltage system having a plurality of module loads is disclosed in the co-pending application of Eldred H. Comstock, Jr., and Raymond G. Martin, entitled, Interlock System, which was filed September 18, 1962, and accorded Serial Number 224,581. In this invention, when there is a fault, the circuit breaker, which is located in the input line to the high voltage power supply that is feeding the fault, is unlocked, thus opening the circuit breaker and the key is then removed and taken to the fault area. The same key is then used to actuate a second look which secures a locking bar against rotation. After unlocking, the locking bar is rotated one-quarter revolution, which then trees a plurality of locking rings which can then be individually rotated. A plurality of connectors, which connect one each to separate loads, are individually connected to separate locking rings through arms. Rotation of the locking ring causes rotation of the arms which, in turn, causes the connectors to be separated from their loads. Rotation of the locking bar also causes a switch to be actuated that is electrically connected between the high voltage power supply and a group of loads.

In the present invention, a circuit breaker lock must first be actuated so that the key can be removed to be used in a second lock. This circuit breaker is positioned in a high voltage line that feeds power to the modules and the key can only be removed when the circuit breaker is open, that is, when the power is interrupted. The key can they be used to open a second lock which releases a latch from a locking bar, which can then be rotated to swing a plurality of tabs out of position so that the plug-in type modules can be removed from their connectors. The modules are connected in series with a second source of voltage and a solenoid coil, and upon removal of any one of the modules, the current to this coil is interrupted which permits a solenoid plunger to drop down and prevent counter-rotation of the locking bar. The second lock is designed such that the key can only be removed when the lock is engaged with the locking bar. Therefore, until all the modules have been replaced and the solenoid actuated, the key cannot be removed from the second lock and thus the first lock cannot be operated to turn on the high voltage power.

It is therefore a general object of the present invention to provide an improved interlock system for use with a plurality of electrical loads.

Another object of the present invention is to provide an interlock system that provides access to a plurality of loads only when a source of high voltage is disconnected from said loads.

Still another object of the present invention is to provide an interlock system that will prevent high voltage to be applied to a group of modules when any one of said modules has been removed from its designated position.

Gther objects and advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

FIGURE 1 is a wiring schematic of one embodiment of the present invention;

FIGURE 2 is a front view, partially broken away, showing a preferred embodiment of the present invention;

FIGURE 3 is a side view of the embodiment shown in FIGURE 2 of the drawing;

FIGURE 4 is a view similar to FIGURE 2 of the drawin-g showing the embodiment in an unlocked position; and

FIGURE 5 is a sectional view taken on line 55 of FIGURE 2.

Referring now to the drawing, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIGURE 1 a source of high voltage V which is connected through a circuit breaker 11 to loads 12 and 13. It should be understood, of course, that a greater or lesser number of loads may be used without departing from the scope of the invention. A source of low voltage V is also connected to loads 12 and 13 and a solenoid coil 14 is connected in series with the loads and the source of low voltage V A switch 15, the operation of which is hereinafter more fully described, is connected in the high voltage line to ground a load before its removal.

Referring now to FIGURES 2-5, there is shown a locking bar 21 that is rotatably mounted to frame 22 by means of bearings 23 and 24. Lock 25, which is mounted on frame 22, is provided with a latch 26 that is engagable with a hole or detent 27 in locking bar 21. The key that operates lock 25 also operates circuit breaker 11, which is designed such that the key can only be removed when the circuit breaker is open. Lock 25, on the other hand, is designed such that the key can only be removed when latch 26 is extended into detent 27.

Bracket 28 is attached to frame 22 and supports connectors 31, 3-2, and 33. Loads 12 and 13 are shown as plug-in modules 34 and 35 and switch 15 is shown as a plug-in module 36. Arms 37 and 38, which are attached to locking bar 21, lightly engage the ends of modules 34 and 35, respectively, and prevent the removal of these modules when locking bar 21 is in its locked position, as shown in FIGURE 2 of the drawing. Ring 39 is also attached to locking bar 21 and linkage 41 is connected between ring 39 and switch arm 42. Rotation of ring 39 actuates switch arm 42 to open and close switch 15.

A solenoid 43 is attached to frame 22, and as shown in FIGURE 1 of the drawing, the solenoid coil 14 is connected in series with loads 12 and 13. Solenoid bar 44 is attached to locking bar 21 in a position such that it will freely pass under solenoid plunger 45 when solenoid 43 is energized. However, when solenoid 43 is deenergized, plunger 45 will drop downwardly, as shown in FIGURE 4 of the drawing, and solenoid bar 44 will not be able to pass under plunger 45. I In operation, first assuming that all modules are in position, with locking bar 21 being in a locked position, as shown in FIGURES 2, 3, and 5 of the drawing, arm 37 prevents the removal of module 34 from its connector 31 and likewise, arm 38 prevents the removal of module 35 from its connector 33. In order for the high voltage V to be applied to the modules, circuit breaker 11 must be closed, and its key cannot be removed while in this closed position. Voltage V will maintain solenoid 43 in an energized condition with plunger 45 being in a raised position.

Assuming now that module 34 is to heremoved from its connector 31, circuit breaker 11 must first be opened, thus cutting 01? the high voltage V from the modules. The key can now be removed from circuit breaker 11 and used to unlock lock 25 which causes latch 26 to be withdrawn from locking bar 21. The key cannot be removed from lock 25 in its lunlocked condition. Locking bar 21 can now be rotated ninety degrees in a clockwise direction thus causing arms 37 and 38 to swing about and permit removal of the modules. As locking bar 21 is rotated, linkage 4 1 causes switch arm 42 to be actuated and switch 15 is closed, thus grounding the module circuits. Upon removal of module 34 from connector 31, the voltage V is interrupted and, consequently, plunger 45 drops downwardly below the height of bar 44. As long as plunger 45 is in a downward position, locking bar 21 cannot be rotated in a counterclockwise direction and consequently lock 25 cannot be actuated so that its key can he removed. Thus as long asmodule 34 is disconnected from connector 31, the high voltage V cannot be applied to connector 31.

When module 34 is again plugged into connector 31, voltage V is applied to solenoid coil 14 and plunger 45 is retracted. Solenoid bar 44- is then free to pass underneath solenoid 43, and therefore locking bar 21 can be rotated ninety degrees in a counterclockwise direction. Arms 37 and 38 will again lightly engage the ends of modules 34 and 35, respectively, and prevent their removal from the connectors. Lock 25 can now be actuated with latch 26 engaging detent 27 in locking bar 21,

and the key can then be removed and used to close circuit breaker 11.

, In summarizing the safety features of the present invention, it can be seen that locking bar 21 can only be rotated when circuit breaker 11 is opened, and consequently a module can only be removed if no voltage is being applied. Also, once a module has been removed, locking bar 21 cannot be rotated and consequently the key cannot be removed from lock 25 to close circuit breaker 11. This assures that no power will ever be applied to an open connector, that is, a connector which does not have a module attached thereto.

It can thus be seen that the present invention provides an improved interlock system that will prevent high voltage from being applied to a group of modules when any one of said modules is not in position. Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An interlocking system for use with an electrical circuit comprising:

a frame,

.a locking bar rotatably mounted to said frame,

means for locking said locking bar in a fixed position comprising a detent in said locking bar and a master lock having means for retaining a key against release except when said master lock is engaged with said detent,

a plurality of loads removably connected to said frame,

means on said locking bar preventing removement of said loads when said locking bar is locked in said fixed position, and means preventing rotation of said locking bar when one of said loads is removed from said frame. 2. An interlock system for use with an electrical circuit comprising:

a frame, a locking bar rotatably mounted to said frame, means for locking said locking bar in a fixed position comprising a detent in said locking bar and a master lock having means for retaining a key against release except when said master lock is engaged with said detent, a source of high voltage, a second source of voltage, a plurality of loads removably attached to said frame and connected to both said sources of voltage,

means on said locking bar preventing removement of said loads when said locking bar'is locked in said fixed position, and

means connected to said second source of voltage for preventing rotation of said locking bar when one of said loads is removed from said frame.

3. An interlock system for use with an electrical circuit as set forth in claim 2, wherein means preventing rotation of said locking bar when one of said loads is removed from said frame comprises a solenoid attached to said frame and a solenoid bar attached to said locking bar adaptable for engaging the plunger of said solenoid.

References Cited by the Examiner UNITED STATES PATENTS 1,976,609 10/ 1934 Gates 30794 2,068,581 l/1957 Tritle 3l7136 3,033,978 5/1962 Van Dusen 104-115 X MILTON O. HIRSHFIELD, Primary Examiner.

ORIS L. RADER, I. I. SWARTZ, Assistant Examiners. 

1. AN INTERLOCKING SYSTEM FOR USE WITH AN ELECTRICAL CIRCUIT COMPRISING: A FRAME, A LOCKING BAR ROTATABLY MOUNTED TO SAID FRAME, MEANS FOR LOCKING SAID LOCKING BAR IN A FIXED POSITION COMPRISING A DETENT IN SAID LOCKING BAR AND A MASTER LOCK HAVING MEANS FOR RETAINING A KEY AGAINST RELEASE EXCEPT WHEN SAID MASTER LOCK IS ENGAGED WITH SAID DETENT, 